To accomplish stain removal from substrates, such as fabric substrates, peroxide bleaching agents, such as hydrogen peroxide or peracids, are generally used as active oxygen ingredients. Such bleaching agents for use in laundering have been known for many years.
These types of active oxygen ingredients are particularly effective in removing stains, such as tea, fruit and wine stains, from clothing, when used in combination with peracid precursors and/or bleach catalysts.
We have now looked at alternative routes for achieving stain removal. First of all, the molecular oxygen present in the wash liquor was considered. It was however found that said molecular oxygen was not sufficiently effective as such for achieving any observable cleaning result; some form of activation appears to be needed for accomplishing bleaching action.
Accordingly, it is an object of the present invention to provide a cleaning result by applying a process in which molecular oxygen is activated and effectively used for cleaning purposes. It is an other object to provide a cleaning process which is cost-effective and environmentally acceptable. It is a further object to provide a cleaning process which improves hygiene and/or reduces dye transfer.
It was surprisingly found that a cleaning benefit could be obtained by applying a simple process wherein a molecular oxygen activating system is added to an aqueous wash liquor containing a sufficient amount of molecular oxygen for obtaining observable cleaning, and a substrate is treated with the thus-obtained wash liquor. In view of the kinetic inertness of the molecular oxygen as such and its low equilibrium concentration in aqueous solutions, it was not expected that observable substrate cleaning performance could be obtained when applying this process. Significant substrate cleaning and bleaching results could even be obtained in the absence of any usually applied active oxygen ingredient such as perborate, percarbonate or peracids.
In this respect, molecular oxygen is defined as dioxygen in the .sup.3 .SIGMA..sub.g.sup.- triplet ground state. Furthermore, in the context of the present invention, a molecular oxygen activating system is defined as a system which activates molecular oxygen (as defined above) resulting in an observably more efficient reaction with a substrate than would be obtained without said system. In other words, the activating system is defined as a compound or mixture of compounds which interacts with molecular oxygen and thereby increases or induces reactivity between said molecular oxygen and a substrate.